package com.sankuai.velocity;/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.    
 */

import android.util.Log;

import org.apache.velocity.VelocityContext;
import org.apache.velocity.app.Velocity;
import org.apache.velocity.app.event.EventCartridge;
import org.apache.velocity.app.event.MethodExceptionEventHandler;
import org.apache.velocity.app.event.NullSetEventHandler;
import org.apache.velocity.app.event.ReferenceInsertionEventHandler;
import org.apache.velocity.exception.MethodInvocationException;
import org.apache.velocity.exception.ParseErrorException;

import java.io.StringWriter;

/**
 * This class is a simple demonstration of how the event handling
 * features of the Velocity Servlet Engine are used.  It uses a
 * custom logger as well to check the log message stream
 * when testing the NullSetEventHandler
 *
 * @author <a href="mailto:geirm@optonline.net">Geir Magnusson Jr.</a>
 * @version $Id: EventExample.java 463298 2006-10-12 16:10:32Z henning $
 */

public class EventExample implements ReferenceInsertionEventHandler,
        NullSetEventHandler, MethodExceptionEventHandler {

    private static final String TAG = "velocity_event";
    private boolean logOutput = false;
    private boolean exceptionSwitch = false;

    public static void main(String args[]) {
        EventExample ee = new EventExample();
    }

    public EventExample() {
        /*
         *  lets make a Context and add some data
         */

        VelocityContext context = new VelocityContext();
        context.put("name", "Velocity");

        /*
         *  Now make an event cartridge, register all the
         *  event handlers (at once) and attach it to the
         *  Context
         */

        EventCartridge ec = new EventCartridge();
        ec.addEventHandler(this);
        ec.attachToContext(context);

        try {
            /*
             *  lets test each type of event handler individually
             *  using 'dynamic' templates
             *
             *  First, the reference insertion handler
             */

            Log.i(TAG, "Velocity Event Handling Demo");
            Log.i(TAG, "============================");

            String s = "The word 'Velocity' should be bounded by emoticons :  $name.";

            StringWriter w = new StringWriter();
            Velocity.evaluate(context, w, "mystring", s);

            Log.i(TAG, "Reference Insertion Test : ");
            Log.i(TAG, "   " + w.toString());
            Log.i(TAG, "");

            /*
             *  using the same handler, we can deal with
             *  null references as well
             */

            s = "There is no reference $floobie, $nullvalue or anything in the brackets : >$!silentnull<";

            w = new StringWriter();
            Velocity.evaluate(context, w, "mystring", s);

            Log.i(TAG, "Reference Insertion Test with null references : ");
            Log.i(TAG, "   " + w.toString());
            Log.i(TAG, "");

            /*
             *  now lets test setting a null value - this test
             *  should result in *no* log output.
             *  Turn on the logger output.
             */

            logOutput = true;

            s = "#set($settest = $NotAReference)";
            w = new StringWriter();

            Log.i(TAG, "NullSetEventHandler test : ");
            System.out.print("      There should be nothing between >");
            Velocity.evaluate(context, w, "mystring", s);
            Log.i(TAG, "< the brackets.");
            Log.i(TAG, "");

            /*
             *  now lets test setting a null value - this test
             *  should result in log output.
             */

            s = "#set($logthis = $NotAReference)";
            w = new StringWriter();

            Log.i(TAG, "NullSetEventHandler test : ");
            System.out.print("     There should be a log message between >");
            Velocity.evaluate(context, w, "mystring", s);
            Log.i(TAG, "< the brackets.");
            Log.i(TAG, "");

            logOutput = false;

            /*
             *  finally, we test a method exception event - we do this
             *  by putting this class in the context, and calling
             *  a method that does nothing but throw an exception.
             *  we use a little switch to turn the event handling
             *  on and off
             *
             *  Note also how the reference insertion process
             *  happens as well
             */

            exceptionSwitch = true;

            context.put("this", this);

            s = " $this.throwException()";
            w = new StringWriter();

            Log.i(TAG, "MethodExceptionEventHandler test : ");
            System.out.print("    This exception will be controlled and converted into a string : ");
            Velocity.evaluate(context, w, "mystring", s);
            Log.i(TAG, "   " + w.toString());
            Log.i(TAG, "");

            /*
             *  now, we turn the switch off, and we can see that the
             *  exception will propgate all the way up here, and
             *  wil be caught by the catch() block below
             */

            exceptionSwitch = false;

            s = " $this.throwException()";
            w = new StringWriter();

            Log.i(TAG, "MethodExceptionEventHandler test : ");
            Log.i(TAG, "    This exception will NOT be controlled. "
                    + " The next thing you should see is the catch() output ");
            Velocity.evaluate(context, w, "mystring", s);
            Log.i(TAG, "If you see this, it didn't work!");

        } catch (ParseErrorException pee) {
            /*
             * thrown if something is wrong with the
             * syntax of our template string
             */
            Log.i(TAG, "ParseErrorException : " + pee);
        } catch (MethodInvocationException mee) {
            /*
             *  thrown if a method of a reference
             *  called by the template
             *  throws an exception. That won't happen here
             *  as we aren't calling any methods in this
             *  example, but we have to catch them anyway
             */
            Log.i(TAG, "   Catch Block : MethodInvocationException : " + mee);
        } catch (Exception e) {
            Log.i(TAG, "Exception : " + e);
        }
    }

    /**
     * Event handler for when a reference is inserted into the output stream.
     */
    public Object referenceInsert(String reference, Object value) {
        /*
         *  if we have a value
         *  lets decorate the reference with emoticons
         */

        String s = null;

        if (value != null) {
            s = " ;) " + value.toString() + " :-)";
        } else {
            /*
             * we only want to deal with $floobie - anything
             *  else we let go
             */
            if (reference.equals("floobie")) {
                s = "<no floobie value>";
            }
        }
        return s;
    }

    /**
     * Event handler for when the right hand side of
     * a #set() directive is null, which results in
     * a log message.  This method gives the application
     * a chance to 'vote' on msg generation
     */
    public boolean shouldLogOnNullSet(String lhs, String rhs) {
        if (lhs.equals("$settest"))
            return false;

        return true;
    }

    public Object methodException(Class claz, String method, Exception e)
            throws Exception {
        /*
         *  only do processing if the switch is on
         */

        if (exceptionSwitch && method.equals("throwException")) {
            return "Hello from the methodException() event handler method.";
        }

        throw e;
    }
}
